Final Fantasy Hacktics

Hello! I've been playing the mod and I'm really enjoying it. I'm having a little trouble getting dark knight to unlock. I have black mage and knight mastered, though I used to cheat to do this (Knight is lvl6 and BLM is lvl1, but all abilities mastered. I just don't have the time to grind and wanted to play DRK lol). I have had the unit kill 20 units until they crystalize/treasurize, but no DRK. Is it locked behind a chapter on top of the regular requirements? Do I need to level Knight and BLM to 8? TIA